Method of making a non-metallic cast chill

ABSTRACT

A METHOD OF AND MEANS FOR PRODUCING THE VARIOUS ELEMENTS OF A METAL FORMING MOLD, SUCH AS A COPE, DRAG, CORE, AND/OR CHILL, BY CASTING EACH ELEMENT FROM AN IMPROVED HIGH TEMPERATURE RESISTANT CASTING COMPOSITION AND THEREAFTER TREATING THE METAL FORMING SURFACES OF EACH CAST ELEMENT WITH A MIXTURE OF PHOSPHORIC ACID AND FURFURYL ALCOHOL RESIN TO HARDEN THE SURFACES AND IMPREGNATE THE LATTER WITH CARBON. A METHOD OF AND MEANS FOR PRODUCING A CAST FOUNDRY CHILL INVOLVING SEALING THE OPEN END OF A CHILL FORM TO A SELECTED SURFACE REGION OF A PATTERN, FILLING THE FORM WITH A CHILL CASTING COMPOSITIN, AND CURING THE COMPOSITION TO PROVIDE A FINISHED CHILL FOR USE IN SUBSEQUENT MOLDING OF A PART IN A MOLD CAVITY CONFORMING TO THE PATTERN.

1972 J. J. VALENTINE METHOD OF MAKING A NON-METALLIC CAST CHILL 3Sheets-Sheet 1 Filed NOV. 26, 1969 L/QU/DS Fred. 2.

L/QU/DS /A/ l/E'A/ TOR JOHN J. MLEA/T/NE A 7'7'0E/VE Y i I ll V/BRA 70/?Feb. 22, 1972 J. J. VALENTINE METHOD OF MAKING A NON-METALLIC CAST CHILL3 Sheets-Sheet 2 AC/D ETHYL 5 AC/D (3: /N70 /50PROP)/L WA TE/Q ALCOHOLAC/D AND WATER nvm ETHYL 5 & lSOPROPYL ALCOHOL Z/RCON/UM cuT MAGNESIUMCARBON 5/L/CA7E GLASS OXIDE WATER WATER /A/7O B NOE R L/QU/DS INTO DRYlNGRED/ENTS 55 /0 i M FIN ,{ww i I A:

- L LL H L 'yL Ol/EA/ I U'iiHl; "mm "run-h Z4 V/BRATOR /A/l/EA/7'02 54JOHN J. VALENTINE fli r! A TraQA/EY United States Patent Olhce 3,644,608Patented Feb. 22, 1972 US. Cl. 264-71 8 Claims ABSTRACT OF THEDISCLOSURE A method of and means for producing the various elements of ametal forming mold, such as a cope, drag, core, and/or chill, by castingeach element from an improved high temperature resistant castingcomposition and thereafter treating the metal forming surfaces of eachcast element with a mixture of phosphoric acid and furfuryl alcoholresin to harden the surfaces and impregnate the latter with carbon. Amethod of and means for producing a cast foundry chill involving sealingthe open end of a chill form to a selected surface region of a pattern,filling the form with a chill casting composition, and curing thecomposition to provide a finished chill for use in subsequent molding ofa part in a mold cavity conforming to the pattern.

This application is a continuation-in-part of my co-pending application,Ser. No. 582,832, filed Sept. 29, 1966, and now abandoned and entitledCast Chill and Method and Means for Fabricating Same.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates generally to the metal casting art. The invention relates moreparticularly to a method of and means for casting the various elementsof a metal forming mold, such as a cope, drag, core, and/or chill.

Prior art According to one of its important aspects, the inventionprovides a novel method of and means for casting a chill for a metalforming mold. Another important aspect of the invention is concernedwith a novel method of and composition for casting the various elementsof a high temperature metal forming mold, such as a cope, drag, coreand/or chill and treating the metal forming surfaces of each element toharden the surfaces and impregnate the latter with carbon. The latteraspect of the invention is particularly suited to the production of moldelements for use in casting high temperature alloys, such as titaniumand beryllium alloys.

SUMMARY OF THE INVENTION The use of chills is a well establishedpractice in the molding or casting art. For this reason, the technologyof chills and the existing techniques of making and using chills neednot be explained in detail. Suflice it to say that the production of asound casting requires flow of adequate liquid metal to all portions ofthe mold cavity to fill the cavity completely as the metal solidifies orfreezes. This, in turn, necessitates progressive solidification orfreezing of the metal in the cavity in such a Way as to assure adequateliquid metal in all portions of the cavity to compensate for thereduction in volume of the metal occasioned by freezing thereof. Unlesssuch proper progressive freezing occurs, the finished cast part may beand generally is defective. For example, a mass of molten metalinherently tends to solidify or freeze inwardly from all sides towardthe center. Accordingly, if the mass of metal is permitted to freeze inthis inherent fashion, a condition will eventually obtain wherein aninner core of liquid metal is encased in an outer shell of solidifiedmetal. This outer shell blocks flow to the core of the additional liquidfeed metal required to compensate for the reduction in the volume of thecore metal which occurs during its subsequent freezing. In this case,the finished cast part is characterized by undesirable internalporosity, large internal shrinkage cavities, and other deformities.Similarly, if a relatively large section of a mold cavity is fed withliquid metal through a relatively narrow section of the cavity, themetal tends to freeze more rapidly in the narrow cavity section than itdoes in the large cavity section. In this case, if the metal freezesprematurely in the narrow section, flow of additional liquid feed metalto the large cavity section will be blocked. Here again, the finishedcast part is characterized by undesirable internal porosity, largeinternal shrinkage cavities, and other deformities. The same adverseresults obtain when irn proper progressive freezing of the liquid metaloccurs in the cavities. The problems discussed above are particularlyserious when the metal being cast is one, such as aluminum, which has arelatively high coefiicient of thermal expansion owing to the fact thatsuch a metal undergoes a relatively large reduction in volume as itfreezes.

In some cases, the proper progressive freezing of liquid metal within amold cavity necessary to the production of a sound casting may beinduced solely by proper design of the casting and utilization of theproper riser ring, gating, and pouring techniques. In other cases, theproduction of a sound casting requires, in addition, selective chillingof the mold cavity. Generally speaking, such chilling involves the rapidconduction of heat away from selected portions of a mold cavity, therebyto establish within the cavity a temperature gradient, or temperaturegradients, which induce proper progressive freezing of the metal withinthe cavity. Thus, the basic aim of chilling is to induce an initialfreezing of the metal at a selected location or selected locationswithin a mold cavity remote from the riser or risers, such thatprogressive freezing of the metal occurs toward and terminates at therisers. In this way, sufiicient liquid peat metal is continuouslyavailable at the advancing front of the freezing metal to compensate forthe reduction in volume of the metal occasioned by freezing.

Selective chilling of a mold cavity may be accomplished in various ways.The present invention is particularly concerned with the chillingtechnique which involves the placement of thermally conductive plugs,commonly referred to as chills, within the mold. One important aspect ofthe invention, for example, relates to an improved chill which avoidscertain of the inherent disadvantages of the existing chills. Thus, theexisting chills are commonly constructed of metal, such as aluminum,iron, copper, or other metal having a sufiiciently high melting pointand coefiicient of thermo conductivity. In some cases, carbon blocks areemployed as chills. These chills are coated with a suitable partingagent, such as a ceramic composition, to prevent adherence to the chillsof the metal being cast. The ceramic or other parting agent is commonlyapplied to the chills by spraying or brushing. After each part is cast,the conventional metal chills are removed from the mold, cleaned, andrecoated with parting agent to condition the chills for reuse. In theevent that a chill incurs damage in use, which happens quite frequently,owing to the rough manner in which the chills are commonly handled, thedamaged chill must be repaired or refaced. The steps incident to initialfabrication of the existing chills, conditioning of the chills forreuse, and repair of damaged chills are time consuming and involvesubstantial cost. Moreover, the number of chills which are unavailablefor use at any given time, due to reconditioning or repair, may be quitelarge. As a consequence either a supply of spare chills, sulficient tosatisfy production requirements, must be maintained at all times, or theproduction of finished castings must be temporarily halted until thepreviously used chills are available for reuse. In the first case, thechill production cost is high. In the second case, production delaycosts are high.

As noted earlier, another important aspect of the invention is concernedwith the production of high temperature metal forming molds for hightemperature alloys, such as titanium and beryllium alloys. Heretofore,the various elements of such molds, such as the drag and cope, have beenproduced by two different methods. According to one method, each moldelement is constructed from a carbon block which is machined to thedesired shape. According to the other method, each mold element is castusing a mixture of a furfuryl alcohol resin and powdered carbon orgraphite.

It is a general object of the present invention to provide a novelnon-metallic cast chill, as well as a novel method of and means forproducing the chill by casting the latter in direct contact with apattern of the part to be molded, and a chill casting composition.

Another object of the invention is to provide a nonmetallic cast chillof the character described which may be conveniently produced insufficient quantity and at sufficiently low cost to render the chilldisposable or reusable, as desired.

Another object of the invention is to provide a nonmetallic cast chillof the character described having an optimum shelf life, whereby anumber of chills may be stored for long periods of time withoutdeterioration, thus to provide a constant available supply of the chillsand thereby eliminate casting production delay time due to theunavailability of chills.

Another object of the invention is to provide a method of and anon-metallic composition for producing the various elements of a hightemperature metal forming mold, such as a cope, drag, core, and/or chillfor high temperature metals such as titanium and beryllium alloys bycasting each element from the composition and then treating its surfacesto harden the surfaces and impregnate the latter with carbon.

Other objects, features and advantages of the present invention willbecome apparent to those versed in the art from a consideration of thefollowing description, the appended claims and the accompanyingdrawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates, insemi-diagrammatic fashion, the present method of the means for casting anon-metallic chill according to the invention;

FIG. 2 illustrates an oven in which the cast chill is cured during thefinal step of the method;

FIG. 3 is a vertical section through the cope of a molding flaskillustrating a finished chill according to the invention positioned inthe cope and the latter being packed with molding sand in preparationfor a casting operation;

FIG. 4 is a vertical section through the completed mold containing thechill;

FIG. 5 is a flow diagram of the present chill casting method; and

'FIG. 6 is a fiow diagram of the present method of producing hightemperature mold elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is made first to FIGS.1 through 4 of the drawings which illustrate an exemplary method of andmeans for casting a chill 10 according to the invention. It should beunderstood that the chill shape shown, as

well as the means for casting the chill, are intended to be merelyillustrative and not limiting in nature and that the nature may beutilized to cast chills of any desired shape by following the generalsteps outlined below. Moreover, While the invention will be explainedprimarily in connection with foundry or sand casting, it will becomeevident as the description proceeds that the invention may be utilizedto produce a chill for any of the known molding or casting techniques,i.e., sand casting including green sand, dry sand, and CO pressures,permanent mold casting, semi-permanent mold casting, plaster casting,and lost wax investment casting.

With the foregoing discussion in mind, the first step in producing achill 10 according to the invention involves the selection of a pattern12 having the shape of a finish part to be cast. For convenience, theillustrated pattern is shown to have a simple shape including arelatively large, generally semi-spherical portion 14 and a reducedniche 16 extending from the semi-spherical portion. The fiat side of thecasting is secured to a plate 17.

The second step of the present chill forming or casting method involvesthe selection of a surface region on the pattern 12 corresponding to thelocation, in a mold cavity conforming to the pattern, at which chillingwill be required during subsequent casting of a finished part in thecavity to induce proper progressive freezing of liquid metal in thecavity. It is obvious that this mold cavity chill location, and hencethe selected surface region of the pattern, will vary from one patternto another. The selected surface region of the illustrated pattern 12corresponding to the mold cavity location at which chilling will berequired to induce proper progressive freezing of liquid metal in themold cavity is designated by the reference numeral 18. In regard toselection of the surface region 18 of the patern 12, attention isdirected to FIG. 4, wherein it will be observed that the pattern isintended to be employed in conjunction with a core 20 to produce a moldcavity 22 for casting a finished part having an external shapecorresponding to that of the pattern and an internal shape correspondingto that of the core. The mold cavity 22 has an enlargement 24, definedby a recess in the core, for forming a corresponding internalenlargement of a cast part. The mold cavity 22 is formed, in the wellknown way, by first placing the cope section 26 and then the dragsection 28 of a molding a flask 30 on the pattern plate 17, about thepattern 12, and packing the interior of the cope section and dragsection with molding sand 31, thus to form the cope and drag of a mold.After removal of the pattern, the cope and drag are assembled with thecore 20 therebetween, in the manner illustrated in FIG. 4, to define thecompleted mold cavity 22. In actual practice, a pair of patterns 12,secured to opposite sides of a match plate, may be utilized in formingthe mold cavity. During subsequent casting of a finished part in themold cavity 22, the latter is fed with liquid metal through a riser 32which opens to the niche portion of the cavity. The cavity is vented at34 in the usual way. At this point, it will be evident to those skilledin the art that proper progressive solidification or freezing of liquidmetal within the cavity 22 requires chilling of the metal in thevicinity of the cavity enlargement 24. The selected surface region 18 ofthe pattern 12 corresponds to this portion of the mold cavity. I

The third step of the present chill forming or cast ng method involvesthe selection of a chill form 36 having an opening 38 conformingapproximately to the selected surface region 18 of the pattern 12 andbounded by a seating edge 40 having a contour conforming substantiallyto the surface contour of the pattern about such surface region. Theillustrated chill form 36 has the general shape of a truncated pyramidand comprises four tapered wall members or plates 42 placed edge toedge, as shown, and releaseably secured in assembled relation by anyconvenient means 44, as nails, straps, rubber bands, or the like. Thewall members or plates 42 of the chill form 36 may be constructed ofwood, metal, plastic, or any other suitable material. The completedchill form has an opening 46 remote from its opening 38 through whichthe chill casting composition of the invention, to be describedpresently, may be introduced into the form.

According to the next step of the present chill casting method, thechill form 36 is placed in chill casting relation to the pattern 12,wherein the seating edge 40 of the form seats against the surface of thepattern about its selected surface region 18. The juncture between thepattern 12 and the chill form 36 is sealed, to prevent leakage of thecasting composition therebetween, in any con venient way, as by pressingmodeling clay 48 about the chill form in the manner shown.

The final step of the present chill forming or casting method involvesintroduction of the present chill casting composition into the chillform 36 through its opening 46. This composition is then permitted toset in the form, thus to produce a rigid chill according to theinvention, after which the chill is removed from the form and cured inan oven 50. The completed chill 10 has a face 52 conforming to theselected surface region 18 of the pattern 12. In order to preventadherence of the chill casting composition to the pattern 12 and hechill form 36, the selected surface region 18 of the pattern and theinner surfaces of the chill form may be coated with a suitable partingagent, such as petroleum jelly, silicone oil, or the like.

After curing, the chill 10 is ready for use. In such use, the chill issupported in proper position relative to the pattern 12, wherein thechill face 52 is disposed adjacent or in seating contact with theselected surface region 18 of the pattern, during forming of the moldcavity 22 in the manner explained earlier. In the illustrated practiceof the invention, for example, the chill 10 is supported in the cope 26of the molding flask 30, atop the pattern 12 in the manner illustratedin FIG. 3, during packing of the cope with the molding sand to form theupper half of the mold cavity 22. The chill remains imbedded in themolding sand when the pattern is removed from the cope. Accordingly, inthe completed mold of FIG. 4, the chill face 52 is exposed to and formsa wall portion of the mold cavity 22. During subsequent casting ofliquid metal in the mold cavity 22, the chill 10 is effetive to conductheat away from the adjacent portion of the cavity, thus to assure properprogressive solidification or freezing of the metal in the cavity andthereby yield a sound casting.

As noted earlier, one important advantage of the present non-metalliccast chill 10 resides in the fact that it may be produced in sufficientquantity and at sutficiently low cost to render the chill reusable ordisposable, as desired. Disposal of the chill, of course, is desirablefor the reason that it eliminates the need for cleaning and otherconditioning of the chill for reuse, and hence the complicationsattendant to such reconditioning. Moreover, the necessity of repairingchills which are damaged during removal from the molding sand aftercasting is eliminated.

The discussion thus far has related only to the use of the present chillin connection with sand casting. As noted earlier, the present chill maybe used, as well, in any of the other casting techniques, to wit,permanent mold casting, semi-permanent mold casting, plaster moldcasting, and lost wax investment casting. In these other castingtechniques, the chill is supported in the mold in much the same manneras a conventional metal chill. In plaster casting, for example, thechill is properly positioned relative to the pattern and liquid plasteris poured about the chill and over the pattern in such a way that thechill is imbedded in the finished plaster mold. In investment casting,permanent mold casting, and semi-permanent mold casting, the chill ismechanically secured or attached to the mold in an area formed by a coreprint. The chill is thus secured by any suitable means, such as gluingor clamping the chill in position or by retaining the chill in positionwith the aid of weights. As also noted earlier, the present chill may beemployed in any of the known techniques of sand casting, including thegreen sand, dry sand, and CO processes. In the CO process of sandcasting, the chill is positioned relative to the pattern and sand, mixedwith sodium silicate, is rammed about the chill and pattern, in much thesame way as described earlier. CO is then passed through the sand tocause setting of the sodium silicate, thus to provide a relatively hardmold.

A chill casting composition of the invention is composed of thefollowing ingredients combined in the approximate proportions indicated,which proportions may be varied, as explained below, to alter theproperties of the cast chill.

Ingredients:

(1) Ethyl silicate (40% concentration)--26,000 cc. (2) Isopropylalcoholl8,000 cc. (3) Water4,000 cc. (4) Hydrochloric acid (36% acidconcentration)- (5) Ground or powdered carbon2,000 cc. (6) 78 meshzirconium silicate2,000 cc. (optional) (7) Cut glass fiber long)-1 ounce(optional) (8) Magnesium oxide (light fired)1 /2 ounce.

The combined ingredients of items 1 through 4 in the above listconstitute a binder. The ingredients of items 5 through 8 constitute dryingredients or solids. According to the present invention, the binder(items 1 through 4) is diluted with water in the approximate proportionsof 2,000 cc.. binder, 4,000 cc. water, to form a diluted binder mixture,and this mixture is combined with the solids (items 5 through 8) to formthe final casting composition of the invention which is introduced intothe chill form 36. According to the preferred practice of the invention,as it is illustrated in FIG. 5, the ethyl silicate and isopropyl alcoholof items 1 and 2 are mixed and stored as are the water and hydrochloricacid of items 3 and 4, since these mixtures are stable and have anindefinite storage life. These two separate mixtures are then combinedbefore use to form the binder. These two mixtures, upon combination,undergo hydrolyzing with resultant generation of heat. According to thepresent invention, the combined mixture, or binder, is permitted to coolto ambient temperature before use. The cooling time of the binder istypically on the order of twelve hours. After cooling, the binder iscombined or diluted with water, as indicated above. Just prior to use,the diluted binder-water mixture is combined with the dry ingredients ofitems 5 through 8 to form the completed casting composition which isthen introduced into the chill form 36.

In carrying out the above steps to produce the casting composition ofthe invention, it is desirable and necessary to mix certain of theingredients in the proper sequence. When mixing the ethyl silicate andisopropyl alcohol, for example, it is immaterial whether the ethylsilicate is added to the isopropyl alcohol or the isopropyl alcohol isadded to the ethyl silicate. However, when mixing the hydrochloric acidand water, it is essential to pour the acid into the water, rather thanthe water into the acid, to avoid the possibility of explosion. Withregard to mixing of the ethyl silicate-isopropyl alcohol mixture and thewater-acid mixture to produce the binder, it is desirable or necessaryto combine these mixtures by pouring the acid-water mixture into theethyl silicate-isopropyl alcohol mixture to avoid very rapid initialhydrolization and resulting jellying of the combined mixture or binder.Mixing of the dry ingredients may be accomplished in any order desired.Preferably, however, the solids of larger proportions, i.e., the carbonand zirconium, are mixed together first, after which the solids of minorproportions, i.e., the cut glass and magnesium oxide are added to thecarbon-zirconium mixture to insure optimum blending of the solids. Thefinal casting composition of the invention, which is produced by mixingthe diluted binder mixture and the solids hardens at a very short periodof time, typically on the order of two to three minutes, whereby thebinder and solids are not mixed until just before casting of the chill,as explained above.

As noted above, the proportions of the various ingredients of thepresent chill casting composition may be varied. For example, thehardness of the binder of the casting composition depends upon thepercentage of ethyl silicate in the binder. In a typical binder mixtureaccording to the invention, the concentration of ethyl silicate is onthe order of 18%. Increasing the concentration of ethyl silicate above18% increases the hardness of the binder. Reducing the concentration ofethyl silicate below 18% reduces the hardness of the binder. Thus, thehardness of the final chill of the invention may be controlled, to adegree, by adjusting the concentration of ethyl silicate in the chillcasting composition. A relatively soft chill, for example, may bedesired in certain applications, such as where an internal chill is tobe removed from a core within a casting. A relatively hard chill, on theother hand, may be desirable where a chill is subjected to rela tivelyhigh pressure, as where a relatively heavy mass of metal is cast aboutthe chill.

The relative hardness or softness of the completed chill may also becontrolled, to some extent, by adjusting the concentration of isopropylalcohol in the chill casting composition. Increasing the proportion ofthis ingredient relative to the ethyl silicate in the composition, forexample, reduces the hardness of the final chill. Similarly, reducingthe proportion of isopropyl alcohol relative to the ethyl silicateincreases the hardness of the final chill.

The concentration of acid in the casting composition affects the rate ofhydrolization which occurs when the binder is mixed with the solidingredients of the casting composition. Increasing the acidconcentration, for example, increases the rate of hydrolization.Similarly, re ducing the acid concentration reduces the rate ofhydrolization.

The zirconium element of the present casting composi tion is employedfor its weight, and also because of its heavier or coarser granularstructure. This relatively coarse granular structure of the zirconium isdesirable for the reason that it prevents surface crazing of the finalchill which would occur if such a coarse granular structure were omittedfrom the chill casting composition.

The cut glass fibers of the present casting composition serve asreinforcing elements. Accordingly, the concentration of glass fibers incomposition may be varied, depending upon the desired strength of thefinal chill.

The concentration of magnesium oxide in the casting compositiondetermines the setting rate of the composition. Thus, increasing theconcentration of magnesium oxide accelerates or reduces the setting timeof the composition. Similarly, reducing the concentration of magnesiumoxide retards or increases the setting time of the composition. Thesetting time of the casting composition may be also regulated, to adegree, by varying the concentration of water in the composition.

The relative proportions of binder and dry ingredients or solids in thecasting composition determines the viscosity of the composition in itsinitial fluent condition. Thus, reducing the proportions of the dryingredients has the effect of reducing the viscosity of or thinning thefluent casting composition. Similarly, increasing the proportions of dryingredients has the effect of increasing the viscosity of or thickeningthe fluent casting composition. A fluent casting composition ofrelatively low viscosity may be desirable, for example, to permitcasting of a chill with relatively fine detail. In other applications, arelatively aviscous chill casting composition may be preferred.

When introducing the fluent casting composition of the invention intothe chill form 36, to cast a chill 10 according to the invention, it isimportant that no air be trapped between the chill composition and thesurface of the pattern 12 in order to avoid the formation of a roughface 52 on the chill. Such a rough chill face, of course, would producea correspondingly rough surface on the cast part in the region of thechill. Such air entrapment may be prevented in various ways. Forexample, the surface region 18 of the pattern which is contacted by thechill casting composition may be initially coated with such composition,as by brushing, prior to actual casting of the chill. Alternatively, thecasting composition Within the chill form may be agitated, as by avibrator 54, during casting of the chill.

As noted earlier, the final step of the present chill cast ing methodinvolves curing of the set chill composition within the oven 50.According to typical practice of the invention, curing is typicallyaccomplished at 350 F. over a period of approximately twelve hours.

As stated earlier, the chill casting technique and casting compositiondiscussed above constitute one important aspect of the invention.Another important aspect of the invention is concerned with theproduction of high temperature mold elements to be assembled into a moldfor use in casting high temperature metals, particularly titanium andberyllium. FIGURE 6 shows a flow diagram depicting this latter inventiveaspect as it is practiced to produce the drag 28a of a metal formingmold. According to this inventive aspect, the same ingredients used toform the chill 10 are mixed in the proportions and in the mannerexplained earlier in connection with the chill to form a castingcomposition. In this regard, it should be noted that mixing the ethylsilicate, isopropyl alcohol, water and acid as we discussed in theearlier description and illustrated in the how diagram of FIGURE 5produces the hydrolyzed ethyl silicate mixture represented by the largebox in the upper left hand area of the fiow digrarn of FIGURE 6. Theresulting casting composition is then poured into the lower drag sectionof the molding flask 30, about the lower half of the pattern 12, andallowed to set, after which the pattern is removed to form the drag 28a.

The next step of method involves treating the metal forming surfaces ofthe drag 28a, i.e., the surfaces of the mold cavity produced by thepattern 12, with an agent which hardens these surfaces and impregnatesthe latter with carbon. According to the present invention, the agentused for this purpose is a mixture of phosphoric acid and furfurylalcohol no-bake resin combined in the following proportions:

Parts phosphoric acid 1 Furfuryl alcohol} 10 No-bake resin In the caseof the drag 28a under discussion, the above mixture is poured into thedrag mold cavity as shown in FIGURE 6 and allowed to remain in thecavity for several minutes. During this time, the mixture permeates thewalls of the cavity. The excess mixture is then poured from the moldcavity and the drag is placed in an inert gas oven 50a and heated to acuring temperature on the order of 1500 F. at a rate of temperatureincrease on the order of F. per hour. The drag is then heated at thefinal curing temperature of 1500 F. for a period of about four hours.This curing action hardens the resin which impregnates the surface ofthe drag mold cavity. The furfuryl alcohol in the resin also impregnatesthe cavity surfaces with carbon. These hard, carbon impregnated walls ofthe drag 28a adapt the latter for molding high temperature metals,particularly titanium and beryllium alloys.

While the above discussion deals with forming the drag 28a of a hightemperature metal forming mold, it is evident the same procedure may befollowed to produce the cope of the mold. Moreover, a core and chill forthis high temperature mold may be produced in essentially the samemanner except that casting composition is formed to the desired shape ina mold cavity rather than about a pattern and the surfaces of the coreand chill are treated with the acid-resin mixture by a clipping orcoating technique rather than by the pouring technique referred toabove.

Those versed in the art will appreciate that the present inventionachieves the objects and realizes the advantages hereinbefore mentioned.

Although a specific embodiment of the present invention has beenillustrated and described herein, it will be understood that the same ismerely exemplary of presently preferred embodiments capable of attainingthe objects and advantages hereinbefore mentioned, and that theinvention is not limited thereto; variations will be readily apparent tothose versed in the art, and the invention is entitled to the broadestinterpretation within the terms of the appended claims.

The inventor claims:

1. The method of making a non-metallic cast chill to be used in castinga finished part in a mold cavity, which comprises the steps of:

selecting a pattern having the shape of the finished part,

selecting a surface region on said pattern corresponding to the regionof said mold cavity where chilling is required,

selecting a fluent settable non-metallic thermally conductive chillcasting composition comprising the following ingredients combined inapproximately the proportions indicated:

hydrolyzed ethyl slicate48,l50 cc.

powdered carbon-2,000 cc.

fibers-l ounce magnesium oxide (light fired)-l% ounce,

casting said composition to a desired chill shape with said compositiondisposed in contact with said surface region of said pattern, and

curing said composition at a temperature of approximately 350 F. for aperiod of approximately twelve hours to provide a finished chill havinga face corresponding in contour to said surface region of said pattern.

2. The method according to claim 1 wherein:

said casting step involves selecting a hollow chill form having anopening conforming approximately to said surface region of said patternand bounded by an edge conforming approximately to the surface contourof said pattern about said surface region, placing said chill form incontact with said pattern in such a way that said chill form edge seatsagainst said pattern about said surface region, and introducing saidcasting composition into said chill form.

3. The method according to claim 1 wherein:

said hydrolyzed ethyl silicate comprises the following ingredientscombined in approximately the proportions indicated:

ethyl silicate-26,000 cc.

isopropyl alcohol-18,000 cc.

water-4,000 cc.

hydrochloric acid-36% concentration-150 cc.

said ingredients are combined to form said casting composition byinitially combining said ethyl silicate and isopropyl alcohol to form afirst liquid mixture and combining said water and acid to form a secondliquid mixture, thereafter combining said liquid mixtures to form abinder, thereafter combining said binder with water to form a dilutedbinder, and thereafter combining said diluted binder with said carbon,fibers, and magnesium oxide to form said casting composition.

4. The method according to claim 1 including the additional step of:

coating said selected surface region of said pattern with a thin layerof said casting composition prior to casting of said chill, thereby toprevent entrapment of air between said casting composition and saidsurface region.

5. The method according to claim 1 including the additional step of:

vibrating said casting composition during setting thereof to prevententrapment of air between said casting composition and said selectedsurface region of said pattern.

6. The method of producing an element, such as a cope, drag, core orchill, for a high temperature metal casting mold which comprises thesteps of:

preparing a casting composition comprising the follow ing ingredientscombined in approximately the proportions indicated:

hydrolyzed ethyl silicate48,l50 cc.

powdered carbon-2,000 cc.

fibers-1 ounce magnesium oxide (light fired)1 /2 ounce,

casting said composition to a desired shape having a surface whichcontacts and forms the molten metal being cast in the mold,

treating said metal forming surface with a mixture comprising thefollowing ingredients combined in approximately the proportionsindicated:

% phosphoric acid-1 part furfuryl alcohol no-bake resin-1O parts,

curing the treated element casting by heating the latter to about 1,500F. at a rate of about per hour and holding the l,500 F. temperature forabout four hours.

7. The method according to claim 6 wherein:

said element casting has a cavity the wall of which provides said metalforming surface, and

said treatment step involves filling said cavity with said treatmentmixture and after a few minutes pouring the excess mixture from saidcavity.

8. The method according to claim 6 wherein:

said metal forming surface of said element is en external surface, and

said treatment step involves coating said surface with said treatmentmixture.

References Cited UNITED STATES PATENTS 1,768,546 7/1930 Curtis 264-712,303,303 11/1942 Schleicher 264-333 2,703,913 3/ 1955 Hinde 264-2202,897,572 8/ 1959 Hansen 264-71 3,060,543 10/ 1962 Shaw 264-71 3,213,49710/1965 Scott 264-225 3,366,720 1/ 1968 Burger 264-333 3,371,135 2/1968Goodwin 264-71 DONALD J. ARNOLD, Primary Examiner US. Cl. X.R.

